Speaking at an official ceremony, the President said that George Koval had made an immense contribution to strengthening Russia’s defence capability.

Mr Koval, who died in 2006 at the age of 94, was the only Soviet intelligence officer to penetrate the U.S. secret atomic facilities producing the plutonium, enriched uranium and polonium used to create the atomic bomb.

Despite the top–secret regime at the facilities and strict control over staff, Mr Koval managed to send descriptions of the sites back to Moscow, along with information on their areas of work and the processes and production volumes of the elements in question.

Mr Koval, who operated under the pseudonym Delmar, provided information that helped speed up considerably the time it took for the Soviet Union to develop an atomic bomb of its own, thus ensuring the preservation of strategic military parity with the United States.

A presidential decree has awarded Mr Koval the Hero of the Russian Federation decoration (posthumous) for his courage and heroism while carrying out special missions.